A search engine returns results that match a search query submitted by a user. General search engines, such as Google, are Crawler-based, as they “crawl” the web to collect information, “index” the information, and allow users to query the index to search through the information. Users often need to find and access information in various content repositories, such as line of knowledge bases, social networks, online news, online video, online music, web search engines, etc. In many situations, a single general search engine may not meet the users' individual requirements to retrieve information in many situations, such as due to lack of access to some content repositories. A federated search engine searches on multiple content repositories and/or information sources. It resolves the deficiency of one search engine and provides a mechanism that allows users to get information gathered from multiple sources. It usually dispatch the users' queries to the underlying content repositories/information sources, utilize their native search function to return results, and then gather and process these results to return to the users. Such a mechanism also eliminates the necessity for information crawling and indexing.